From: Chris Lee <c_h_r_i_s_l_e_e@...>
Date: 2007-08-03T13:20:05+09:00
Subject: Re: public key encrypt

Sonn Ygg wrote:
> Sonn Ygg wrote:
>> Hello all,
>>
>> I know how to use public key to encrypt data if I create public/private
>> key pair by myself through OpenSSL::PKey::RSA. However, if I only know
>> other guy's public key, how could I encrypt data with his/her public
>> key? Is there any method in the module OpenSSL::PKey::RSA to support it?
>> Thanks!
> 
> Does any one can help me about this question? thanks.

If you're trying to do GPG, there's a module that might help.  If not, I'd have
to research this closely as the documentation for OpenSSL is lacking.

require 'gpgme'

  def get_pgp_keys emails
    # this function searches your GPG keyring for valid public keys for
    # each of the email addresses listed in emails
    # if a key is not found for an email, it will be omitted from the output list
    ctx = GPGME::Ctx.new
    keys = []
    emails.each do |email|
      begin
        ctx.keylist_start email
        key = ctx.keylist_next
        ctx.keylist_end
        keys << key
      rescue EOFError
        # the key for this email was not found and keylist_next threw this error
        # this is expected behavior when there was no key found for the email
address
      end
    end
    keys
  end

      # check list with gpg
      keys = get_pgp_keys to_emails

      plaintext = @body.join ""
      # if all match, encrypt @body
      if keys.size == to_emails.size
        keys << Redwood.get_personal_public_key
        ciphertext = GPGME.encrypt keys, plaintext, {:armor => true, :sign =>
true, :passphrase_callback => getpass }
        @body = ciphertext.split "\n"
        @body.map { |l| l+"\n" }
      else
        GPGME.sign plaintext, nil, { :mode => GPGME::SIG_MODE_CLEAR }
      end
    end